The Diocese of Parramatta is the Catholic Church in Western Sydney and the Blue Mountains.

It spans one of the fastest-growing areas of Australia, incorporating the greater Western Sydney area from Parramatta to Blackheath and from Richmond to Warragamba. It is home to 330,000 Catholics in an area of 1,050,000 people.

The Diocese hosts 47 parishes and churches, educates more than 45,000 students across its 83 schools, employs more than 5,000 staff and cares for thousands of people in need through its social services arm, CatholicCare Social Services.

The Diocese of Parramatta is the fifth-largest Catholic Diocese in Australia.